The need to suitably protect cables in aircraft from electromagnetic fields created by lightning, which particularly translates into transitory current and voltage drops, is known in the aeronautical industry.
Up until a few years age, metallic materials (for example aluminum) were used in the aeronautical field as the primary material of aircraft structures. Having a large amount of said materials in the airplane involved a good grounding of the systems and made the airplane have a rather good electrical continuity and relatively low electrical resistance values, thus preventing potential drops, relevant structural damage, the presence of burning or incandescent particles or hot gases released at the point of contact between two conductors when a large current density passed (sparking), and overheating of the material due to the direct striking of lightning or for being subjected to a high current density (hot-spot).
The vertiginous evolution towards aircraft structures built with carbon fiber has caused that the damage occurring in this type of material as a result of its heterogeneous features are considerable and to be taken into account due to its criticality.
In aircrafts built with carbon fiber, the traditional bonding concept in an airplane, known as a primary metallic structure, tends to disappear and the traditional protection methods are no longer applicable.
Providing a structure built with carbon fiber means that in case of lightning strike, from the electromagnetic point of view, the systems and equipment enclosed by said structure are more vulnerable and are therefore more exposed to induced effects, which basically translate into transient current and voltage drops. These transient states normally affect the wiring and take place as a result of the magnetic field created by the current of the lightening circulating through the outer structure.
“Hybrid” solutions, which combine electrical bonding to a metallic structure and to carbon fiber, are currently known to resolve these problems.
In particular, to protect the cable bundles installed in areas with a composite catalogued as “exposed areas” for these purposes, a shielding or metal braid minimizing the induced effects in the cables of said bundles is added. This shielding is generally electrically bonded at both ends appropriately since this is the most critical point of the installation (for the purpose of having good electromagnetic protection) and when the routes exceed 3 meters, an “intermediate bonding point” must be installed, connecting the shielding to a metallic structure every 3 meters.
The inability in some cases of having sufficient metallic structure, or the lack of closeness between the systems installed in the airplane and the metallic structures thereof, makes it necessary to install additional bonding strips and bonding jumpers, increasing airplane costs and weight.
This invention proposes a solution to this drawback.